Landing gear control system



April 13, 1943 M. J. FINNEGAN LANDING GAR CONTROL SYSTEM Filed May 31, 1941 2 Sheets-Sheet l April 13, l943 l M. J. FINNEGAN 2,316,682

LANDING GEAR CONTROL SYSTEM Filed May 31, 1941 2 Sheets-Sheet 2 Patented Apr. 13, 1943 Martin J. Finnegan, Glen Rock, N. J.,

to Bendix Aviation Corporation, South assignor Bend,

Ind., a corporation of Delaware Application May 31', 1941, Serial No. 396,149

3 Claims.

This invention relates to the control of the landing gear of aircraft, and more particularly to a system for automatically positioning the landing gear in accordance with certain flight indications.

One of the hazards' of flight in craft with retractable landing gear has been the possibility of landing with the wheels retracted, due to the forgetfulness of the pilot, or to his preoccupation with the many flight questions involved during a landing maneuver.

It is an object of the present invention to provide a system automatically operated in response to certain flight conditions to extend the retracted landing gear of an aircraft.

It is another object of the invention to provide a means incorporated into lcertain standard flight instruments for controlling the operation of a landing gear motor.

Other objects include the provision of a system automatically responsive to predetermined safe flying conditions for maintaining the gear of an aircraft retracted, and for extending the gear upon the variation from safe condition of certain fiight factors.

Additional objects will appear from a study of the following specification when made in conjunction with the attached drawings, throughout which like numerais designate like parts.

Fig. l is a circuit diagram of one embodiment Vof the present invention, showing the landing gear of an aircraft extended.

Fig. 2 is a showing of the same circuit with the landing gear in retracted position.

Fig. 3 is a plan view of a night instrument m4 corporating a novel feature of the present invention; and

Fig. 4 is an elevational view, partly in section, ofv the instrument shown inv Fig. 3.

In accordance with the present invention, contact means are provided between the pointer and s cale df an air speed indicator and of an'altimeter for completing a circuitwhen altitude and air speed indications lie within a certain range, for extending, and maintaining extended, the landing gear of the aircraft. Novel circuitmeans are provided for automatically retracting the extended gear, and maintaining it retracted, when the indications of either altitude or air speed exceed a predetermined minimum safe value for level flight.

Having particular reference to Figs'. i and 2,

I0 represents an air speed indicator,-having a pointer II and a contact member I2 extending in an arc for a portion of the circumference of the air speed indicator. An altimeter I3, having a pointer I4, movable with respect to a contact stripv I5, is connected in series with contact member I2 through a conductor I6 and a current limiting resistor I1. A battery I8 provides electrical energy for energizing a relay I9, which is connected to the pointer I4 of altimeter I3 by.

means of a conductor 20, and to battery I3 through a conductor 2l, while battery I8 is connected in series to the pointer Il of air speed indicator I0 by means of a conductor 22.

' Relay I9 has a front contact 23, a back contact i 24, and an armature 25. A landing gear operating motor 26 has one side of its armature connected to battery I8 through conductor 21, and

has the other side of its armature connected to one end of two oppositely wound series fields 28 and 29. The other end of series field 28 is connected to the stationary pole 39 of a limit switch 3| through a conductor' 32, and switch blade 33 of limit switch 3l is'connected toxback contact 24 by means of a conductor 34. The other end of field 29 is connected to theswitch arm 35 of a limit switch 36, and front contact 23 is connected to the stationary contact 3'l of limit switch 36 through a conductor 38.

As shown in Fig. 1, the landing gear strut 39, which is pivoted at 40, is"vconnected,- by means of any suitable shaft 4 I to the armature of motor 2G in the conventional manner. Strut 39 carries a projecting finger 42, which. as'shown in Fig. 1, engages switch arm 35 to open the circuit of eld 29 when the gear is in the extended position, and as shown in Fig. 2. finger 42 engages switch blade 33v to open limit switch 3| and the circuit of field 28 when the landing gear is in the retracted position.

Figs. 3 and 4 show one means whereby an altimeter and an air speed indicator may have contact members embodied therein for use with the novel system of the present invention. The instrument shown in Figs. 3 and 4 will be described as an altimeter, but it will be understood that the description is equally applicable to an air speed indicator, since the" contact means to be described is the same for each instrument.

Altimeter I3 has a. scale member 43, which, in

-the present instance, may lbe'of non-conducting material, such as Bakelite, bearing indications of altitude in thlousands of feet. A metal sector 44, extending through the angular measure between 'zero and one thousand feet, is held upon scale member 43 in a sliding' friction fit, by means of a circular ange portion 45 that lies behind scale member43. Pointer I4 carries a suit- -able brush member, such as a hair spring 46,

which contacts lightly with metal sector 44. n its back face, scale 43 carries a terminal member 41, which may -be secured in any ordinary way thereto, and a brush member 48 extends therefrom and makes contact' with circular iiange member 45. Terminal member 41 connects with insulated conductor IB, carried in a.

conduit 49 along with insulatedl conductor 20,

which is electrically connected by means of a. suitable brush member 50 to the metal shaft 5I carrying pointer I4. By this construction, whenever pointer I4 lies between 0 and 1 on scale 43, brush member 46 is in contact vwith metal sector 44, and it will be readily seen that a. closed electrical circuit is thus provided. Whenever pointer I4 lies outside of theo and ldesignations of scale 43, brush member 46 is out of contact with sector 44, and therefor, the elec' trical connection within altimeter I3 is broken.

By means of the present invention, a pilot may completely forget to extend his landing gear prior to landing, but whenever his air speed falls below a minimum 'safe' air speed, such as eighty miles an hour, and when his altitude falls below that safe for sustained level flight, for example, one thousand feet, then, by means of the circuit shown in Fig. 1, motor 4I is operated to extend the landing gear as shown in Fig. 1, and upon complete extension, the motor circuit is opened by the engagement of finger 42 with the limit switch 36. It should be noted that when the crafts altitude is' in excess of one thousand feet, andthe air speed is below the safe minimum value, the landing gear will not be extended, since the relay circuit will be opened by pointer I4. It is the two factors of air speed and altitude, which, in combination, determine the necessity of extending the landing gear, and if the air speed falls below eighty miles an hour, and the pilot stili has altitude in excess of one thousand feet, the craft can be dived to increase the air speed to a safe value, or increased power may be delivered suiiicient to re-establish a safe air speed prior to loss of altitude below one thousand feet.

When the aircraft takes oif, the pilot need not be concerned with retracting the landing V gear, since the establishment of van air speed in excess of the safe minimum, even though the a1- titude is considerably less than a. thousand feet, will cause the relay circuit to be deenergized, due to thev open circuit at the pointer II, and as armature 25 falls upon contact 24, the up" eld 28 is energized to retract the landing gear to the positionA shown in Fig. 2, and once the fully retracted position is attained, nger 42 opens the The landing gear control above described is completely electrical, but it will be understood, without more specific illustration, that the circuit may operate a hydraulic servo system for doing the actual extension and retraction of the landing gear. Likewise, the electrical means, if employed, may assume diierent form, such as the use of diilerently constituted motor elements and motor reversing means.

While only one embodiment of the present invention has been shown in the drawings, it is to be understood that various changes may be made without departing from the scope of the present invention. For this reason, it is intended not to limit the invention by the description herein given as an example, but solely by the scope of the appended claims.

I claim:

1. A mechanism for controlling the operation of landing gear comprising a source of electrical energy, a motor energizable therefrom, a switch for closing the energizing circuit for said motor, and a circuit in parallel to the first mentioned circuit including in series, an altimeter, an air speed indicator, a. solenoid and said source of electrical energy, and contact means on said altimeter and said air speed indicator, each extending over a predetermined range of indications for actuating said solenoid to close said switch, thus energizing said motor. v

2. In a systemrfor controlling the retraction and extension of the landing gear of an aircraft, the'combination of an altimeter, an air speed indicator, contact means on said altimeter and said indicator extending over predetermined indicated values of altitude and air speed, a land ing gear motor, circuit connections lbetween said motor and said altimeter and air speed indicator, contact means for extending the landing gear when the indications of both said altimeter and said air speed indicator come Within said predetermined values-and other circuit connections operativenpon the exceeding of said predetermined values of either said altimeter or said air speed indicatorvfor operating said motor to rev tract the landing gear.

3. In a system for controlling the extension and retraction of the landinggear of aircraft, a motor for extending and retracting landing gear, an altimeter, an air speed indicator, contact means for maintaining a closed circuit condition through said altimeter and said air speed indicator over predetermined indicated valuesof altitude and air speed, series connections between said altimeter, said indicator and said motor, whereby when the indication of said altimeter and said speed lie within said predetermined values, said motor will maintain the landing gear extended, and additional circuit means, responsive to indications of said altimeter or of said air speed indicator exceeding said predetermined values, for operating said motor to retract the landing gear.'

' MARTIN J. FINNEGAN. 

